Breast cancer includes subtypes defined by hormone receptors, which indicate varied etiologies, clinical characteristics, and survival rates [i]. There are differing hypotheses regarding how dairy products may influence breast cancer risk [Zhang et al., 2017, Bialek et al., 2013, Davoodi et al., 2013, Hidayat et al., 2016, Harrison et al., 2017 as cited in reference i]. In the below study, the authors explore dairy and calcium intake and risk of overall breast cancer and of estrogen receptor (ER) status subtypes.
Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies
The American Journal of Clinical Nutrition
This pooled analysis of 21 prospective cohort studies from the Pooling Project of Prospective Studies of Diet and Cancer included over 1 million women. Food Frequency Questionnaires (FFQs) were administered at baseline, and the authors looked at total milk, hard cheese, cottage/ricotta cheese, yogurt, and ice cream intake. All 21 studies estimated calcium intake from food, and 12 of the 21 studies estimated calcium intake from food and supplements. The authors administered follow-up questionnaires and reviewed medical records and cancer registries over a period of 8-20 years to identify breast cancer cases and estrogen and progesterone receptor status (ER and PR, respectively) [i].
The authors found:
1. Median calcium intake from food of 490-853 mg per day and median calcium intake from food and supplements of 675-1173 mg per day
2. No significant associations between dairy intake or calcium intake (including food and supplements) and overall breast cancer risk
3. Significant inverse associations between cottage cheese/ricotta cheese intake (25 grams or more per day compared to less than 1 gram per day) and yogurt intake (60 grams or more per day compared to less than 1 gram per day) and ER-negative breast cancer risk
4. A significant inverse trend between calcium intake from food and overall breast cancer risk, although there was no significant association for the highest intake category of 1400 mg per day [i]
For the Patient and Caregiver
To put finding #3 into perspective, one 4 oz container of cottage cheese is 113 grams and one 5.3 oz container of Greek yogurt is 150 grams. Consider pairing these foods with fruit, nuts, or seeds for nutritious snack or mini-meal options. The recommended daily calcium intake is 1000 mg for adult women up to age 50 and 1200 mg for women over 50, and 1000 mg for adult men up to age 70 and 1200 mg for men over 70. To reach 1200 mg of calcium per day, you may eat 8 oz yogurt (415 mg) with 2 Tbsp chia seeds (168 mg), 1 serving of fortified breakfast cereal (130 mg), 1 cup cottage cheese (138 mg), 3 oz canned salmon (181 mg), 1 cup cooked kale (94 mg), and ½ cup cooked turnip greens (99 mg) [ii].
For the Healthcare Team
Dairy products are our main dietary source of conjugated linoleic acid, calcium, and vitamin D in fortified products, which may have anticarcinogenic properties [Zhang et al., 2017, Bialek et al., 2013, Davoodi et al., 2013, Hidayat et al., 2016 as cited in reference i]. Contrastingly, they also contain BCAAs (branched chain amino acids) which may increase IGF-1 (insulin-like growth factor 1) and in turn may promote cell growth and increase DNA replication errors [Harrison et al., 2017, Nachman et al., 2015, Christopoulos et al., 2015 as cited in reference i]. Interestingly, yogurt does not increase IGF-1 as do other dairy products [Romo et al., 2020 as cited in reference i]. In addition, yogurt is fermented and contains probiotics, which may increase microbiome diversity, urinary estrogen excretion, and induce apoptosis of breast cancer cells [Flores et al., 2012, Hassan et al., 2016, Lakritz et al., 2014 as cited in reference i]. Cottage and ricotta cheese also have more bacterial counts compared to hard cheese [Baruzzi et al., 2000, Lovayova et al., 2015, Kok et al., 2018 as cited in reference i]. Additional research including a more diverse population and a closer look at fermented foods would be beneficial, although it may be appropriate to recommend yogurt, cottage cheese, and ricotta cheese to patients as nutritious dairy products rich in calcium.
[i] Wu Y, Huang R, Wang M, Bernstein L, Bethea TN, Chen C…Smith-Warner SA. (2021). Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies. The American Journal of Clinical Nutrition;0:1-12, https://doi.org/10.1093/ajcn/nqab097
[ii] National Institutes of Health. Calcium. https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/